UV-curable nanocasting technique to prepare bioinspired superhydrophobic organic-inorganic composite anticorrosion coatings

A UV-curing technique was used to develop advanced anticorrosive coatings made of a poly(methyl methacry- late) (PMMA)/silica composite (PSC) with bioinspired Xanthosoma sagittifolium leaf-like superhydrophobic surfaces. First of all, a transparent soft template with negative patterns of xanthosoma sagittifolium leaf can be fabricated by thermally cur- ing the polydimethylsiloxane (PDMS) pre-polymer in molds at 60°C for 4 h, followed by detaching PDMS template from the surface of natural leaf. PSC coatings with biomimetic structures can be prepared by performing the UV-radiation process upon casting UV-curable precursor with photo-initiator onto cold-rolled steel (CRS) electrode under PDMS tem- plate. Subsequently, UV-radiation process was carried out by using light source with light intensity of 100 mW/cm 2 with exposing wavelength of 365 nm. Surface morphologies of the as-synthesized hydrophobic PMMA (HP) and superhydropho- bic PSC (SPSC) coatings showed a large number of micro-scaled mastoids, each decorated with many nano-scaled wrinkles that were systematically investigated by using scanning electron microscopy (SEM). The contact angles of water droplets on the sample surfaces can be increased from ~81 and 103° on PMMA and PSC surfaces to ~148 and 163° on HP and SPSC surfaces, respectively. The SPSC coating was found to provide an advanced corrosion protection effect on CRS electrodes compared to that of neat PMMA, PSC, and HP coatings based on a series of electrochemical corrosion measurements in 3.5 wt% NaCl electrolyte. Enhanced corrosion protection of SPSC coatings on CRS electrodes can be illustrated by that the silica nanoparticles on the small papillary hills of the bioinspired structure of the surface further increased the surface rough- ness, making the surface exhibit superior superhydrophobic, and thus leading to much better anticorrosion performance.